Plank was ranked 327 on the Forbes 400 list of wealthiest Americans when it was released in September, with a net worth of $1.7 billion. However, on the latest list, his rank rose to 258 in the country after his net worth increased by $700 million to $2.4 billion.

So what has Mr. Under Armour been up to since September?

Well, his company’s stock, which according to Forbes accounts for most of Plank’s net worth, has risen considerably since September.

On the day of the Forbes 400 release, UA closed at $75.44. It opened Tuesday at $115.75. For Plank, who owns millions of shares, that can create a noticeable difference.